Remove unused material instances before rendering frame.

Also ensure material texture hashes are unique so that the material
cleanup works correctly.

PiperOrigin-RevId: 937206048
Change-Id: Ibed53457ee271f4faae3bcac5fb479b5ce9fc352

src/render/filament/core/filament_context.cc

@@ -94,16 +94,17 @@ mjrfFrameHandle FilamentContext::Render(
 
   ValidateSwapChains(requests);
 
-  material_manager_->BeginFrame();
-
   std::unordered_map<mjrfScene*, std::vector<const mjrfRenderRequest*>>
       scene_to_requests;
   for (const mjrfRenderRequest& request : requests) {
     scene_to_requests[request.scene].push_back(&request);
   }
+
+  material_manager_->PrepareToRender();
   for (auto& [scene, requests] : scene_to_requests) {
     SceneView::downcast(scene)->PrepareToRender(requests);
   }
+  material_manager_->RemoveUnusedMaterials();
 
   bool render_began = false;
   mjrfRenderTarget* current_target = nullptr;
@@ -159,7 +160,6 @@ mjrfFrameHandle FilamentContext::Render(
 
   if (render_began) {
     renderer_->endFrame();
-    material_manager_->EndFrame();
   }
   if constexpr (!UTILS_HAS_THREADING) {
     engine_->execute();

src/render/filament/core/material_manager.cc

@@ -38,6 +38,13 @@ static void Combine(uint64_t& seed, const T* v) {
   seed ^= std::hash<T>()(*v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
 }
 
+static void Combine(uint64_t& seed, const mjrfTexture* texture) {
+  if (texture) {
+    const uint64_t id = Texture::downcast(texture)->Id();
+    Combine(seed, &id);
+  }
+}
+
 template <typename T>
 static uint64_t hash(const T& obj) {
   static_assert(std::is_trivially_copyable_v<T>,
@@ -77,9 +84,9 @@ MaterialManager::~MaterialManager() {
   }
 }
 
-void MaterialManager::BeginFrame() { used_keys_.clear(); }
+void MaterialManager::PrepareToRender() { used_keys_.clear(); }
 
-void MaterialManager::EndFrame() {
+void MaterialManager::RemoveUnusedMaterials() {
   if (instances_.size() == used_keys_.size()) {
     return;
   }
@@ -102,6 +109,15 @@ static MaterialManager::MaterialKey BuildMaterialKey(
   uint64_t key = hash(material);
   Combine(key, &geom_type);
   Combine(key, &material_type);
+  Combine(key, material.color_texture);
+  Combine(key, material.opacity_texture);
+  Combine(key, material.normal_texture);
+  Combine(key, material.orm_texture);
+  Combine(key, material.metallic_texture);
+  Combine(key, material.roughness_texture);
+  Combine(key, material.occlusion_texture);
+  Combine(key, material.emissive_texture);
+  Combine(key, material.reflection_texture);
   return key;
 }
 

src/render/filament/core/material_manager.h

@@ -52,10 +52,10 @@ class MaterialManager {
   // Marks the beginning of a new frame, allowing us to track which
   // MaterialInstances are used during the frame so they can be removed at the
   // end of the frame.
-  void BeginFrame();
+  void PrepareToRender();
 
   // Removes any unused MaterialInstances.
-  void EndFrame();
+  void RemoveUnusedMaterials();
 
   // Returns a MaterialType that best matches the given material data and mesh.
   MaterialType GetMaterialType(const mjrfMaterial& material, const Mesh* mesh);

src/render/filament/core/texture.cc

@@ -14,6 +14,7 @@
 
 #include "render/filament/core/texture.h"
 
+#include <atomic>
 #include <cstddef>
 #include <cstdint>
 #include <cstring>
@@ -28,6 +29,8 @@
 
 namespace mujoco {
 
+static std::atomic<uint64_t> g_next_texture_id{1};
+
 static constexpr int kNumFacesPerCube = 6;
 
 static bool IsCompressed(const mjrfTextureConfig& config) {
@@ -115,7 +118,7 @@ static filament::Texture::InternalFormat GetTextureInternalFormat(
 
 Texture::Texture(filament::Engine* engine, const mjrfTextureConfig& config,
                  InternalFlags flags)
-    : engine_(engine), config_(config) {
+    : id_(g_next_texture_id++), engine_(engine), config_(config) {
   if (IsCompressed(config_)) {
     // We defer creation of compressed textures until Upload() is called. In
     // the meantime, we don't really know anything about the texture (e.g.

src/render/filament/core/texture.h

@@ -15,6 +15,7 @@
 #ifndef MUJOCO_SRC_RENDER_FILAMENT_CORE_TEXTURE_H_
 #define MUJOCO_SRC_RENDER_FILAMENT_CORE_TEXTURE_H_
 
+#include <cstdint>
 #include <filament/Engine.h>
 #include <filament/Texture.h>
 #include <math/vec3.h>
@@ -57,6 +58,9 @@ class Texture : public mjrfTexture {
   // Returns the underlying filament texture.
   filament::Texture* GetFilamentTexture() const { return texture_; }
 
+  // Returns the unique id of the texture.
+  uint64_t Id() const { return id_; }
+
   // Returns any spherical harmonics data associated with the texture.
   using SphericalHarmonics = filament::math::float3[9];
   const SphericalHarmonics* GetSphericalHarmonics() const {
@@ -73,6 +77,7 @@ class Texture : public mjrfTexture {
  private:
   void ReleaseData();
 
+  uint64_t id_ = 0;
   filament::Engine* engine_ = nullptr;
   filament::Texture* texture_ = nullptr;
   mjrfTextureConfig config_;